The track brake does the lion's share of the work. The friction between wood and steel is what primarily stops the car. Make that dry wood and dry steel. Wet equals slick... this is not good.

This is where sand comes to the rescue. A small pedal on the floor is pressed to drop sand on the rails. The wheels crush the sand into powder, the powder soaks up the moisture and provides -- the magic word -- friction!

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The grip goes down into the cable slot to grab the cable, that's the only attachment. From the way it is sitting it looks like the grip is still in the slot of the eastbound track and the rear end came off the tracks. That grip is probably twisted all to hell now, I wonder how they got it out of the slot?

I have spent a long time studying the mechanisms of the cable cars because cable car is the is easiest way to get to my apartment. What really impresses me is the actual cable-grabbing mechanism, it's something you can't see from the car because its under the street -- they have a lot of examples at the cable car museum. I highly recommend going to the cable car museum to see the cable vaults too. It's free and full of massive wheels, gears and turn of the century mechanisms. They build all those cable cars by hand.

The grip twisted unless it just tore off of whatever holds it to the car, but I also wonder if there is enough play in the slot to put a kink in the cable--that would be bad. Seems like the cable slot could be damaged too.

From the jaunty attitude of the car in the photo, and the circular skid marks, it is clear that the operator was actually doing donuts. Bravo to him/her.

And tjcrowley is right about the cable grips, and the fact that you should go to the cable car museum. I went the first time I ever came to SF, and ever since I've had it in my head that skateboarders need their own cable grips so they can hitch a ride up the hills.

My great-uncle once told me about a prank the kids in Chicago would play with the cables. Take a sheet or two of newspaper, and roll it up on the diagonal so it makes a long, flimsy tube. Hold one end, and flick the rest down into the cable slot. If you did it right, the bottom of the tube would wrap around and grab the cable, jerking the paper out of your hand. The part sticking out of the ground would partly unroll, and go rattling down the street, scaring the hell out of all the horses and making them panic.

Almost all rail vehicles--locomotives, light rail vehicles, and multiple unit trains--dispense sand to improve traction for starting and braking; it's no surprise that cable cars have a similar arrangement.

On the light-rail trains here in Los Angeles, the sandboxes are mounted underneath passenger seats at the ends of the cars and have windows to see the sand itself.

Yes, from some highly interesting work I did for a major UK train company (who are also a record label, TV channel and Broadband provider) I know possibly too much about trains and their inner workings.

I can make train spotters wet themselves with glee by describing the logic that prevents the train from moving if its doors are open.

Oh, and these high speed trains also shit sand (and the contents of their holding tanks when they fill up) onto the track.

Trains have holding tanks that the toilets empty into. These get emptied when the train goes to the depot, or at a station.

However if it fills up mid journey they just dump it onto the tracks. There must be a few old trains around that empty onto the tracks anyway as my local station's tracks are covered in bits of toilet roll.

Yeah, for a long, long time railway toilets just opened right onto the tracks. You could look down and see the roadbed going by under the toilet. Modern regulations tend to restrict such things, hence the holding tanks.

The doors have switches in them that open when the doors are open. All the doors are linked together into a safety circuit. If the continuity of this circuit is broken, the train's motor controller is instructed to put the brakes on and turn off the engine (if it's moving) or to keep the brakes on and attempt to close any open doors (if at a station). I think the emergency stop was connected to this as well.

Next time you get in a train, sit near the carriage with the generator and pantograph in it (aptly for this thread it is probably the carriage with the toilet in) and listen. You'll hear half a dozen relays opening and closing as everything is checked, re-checked and locked.

The engines are clever too. When the train is doing anything but accelerating they turn off and turn into dynamos instead, converting the train's motion back into AC current which is fed back into the power grid.

The trams in Melbourne (the new, European ones, not the vintage wooden ones) have transparent windows in the wall panels/under the seats, which show the level of sand in the reservoir. From time to time, the passenger witnesses a sandquake as the bottom of the reservoir falls out.

You can catch a brief video segment on the sand system (for Toronto streetcars) from around 0:40 to 0:50 (a whole 10 seconds!) in this video.

That clip is actually part 3/3 (Part 1 and Part 2) of an episode on Toronto streetcars, from some tv show called Things That Move that apparently airs on the Canadian History Channel. I've never seen the show outside of those clips, but apart from the annoying host the episode itself is mildly interesting.

Something you may or may not want to know about the brakes on the cable cars, they (at least when I was in middle school) are made by middle school students at Marina Middle School. The kids would shape and cut them and burn their names and class into the the block and after it was used MUNI would return the used brake to the school and/or student. I stopped riding them when my friends at Marina showed me the returned, used scorched wood block.